Re: [edk2-devel] [PATCH V1 1/1] MdeModulePkg/Variable: Fix VarErrorFlag RT cache offset calculation

["Wang, Jian J" <jian.j.wang@intel.com>]

Michael,

I'm not sure sync-ing whole variable cache memory is an efficient operation.
What about using mVariableModuleGlobal->NonVolatileLastVariableOffset
as Length parameter?

       Status =  SynchronizeRuntimeVariableCache (
                   &mVariableModuleGlobal->VariableGlobal.VariableRuntimeCacheContext.VariableRuntimeNvCache,
                   0,
                   mVariableModuleGlobal->NonVolatileLastVariableOffset
                   );

Regards,
Jian

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Kubacki,
> Michael A
> Sent: Tuesday, January 14, 2020 7:19 AM
> To: devel@edk2.groups.io
> Cc: Gao, Liming <liming.gao@intel.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; Michael Turner
> <michael.turner@microsoft.com>; Wang, Jian J <jian.j.wang@intel.com>; Wu,
> Hao A <hao.a.wu@intel.com>
> Subject: [edk2-devel] [PATCH V1 1/1] MdeModulePkg/Variable: Fix VarErrorFlag
> RT cache offset calculation
> 
> REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2457
> 
> This commit fixes an offset calculation that is used to write the
> VarErrorFlag UEFI variable to the UEFI variable runtime cache.
> 
> Currently a physical address is used instead of an offset. This
> commit changes the offset to zero with a length of the entire
> non-volatile variable store so the entire non-volatile variable
> store buffer in SMRAM (with the variable update modification) is
> copied to the runtime variable cache. This follows the same pattern
> used in other SynchronizeRuntimeVariableCache () calls for
> consistency.
> 
> * Observable symptom: An exception in SMM will most likely occur
>   due to the invalid memory reference when the VarErrorFlag variable
>   is written. The variable is most commonly written when the UEFI
>   variable store is full.
> 
> * The issue only occurs when the variable runtime cache is enabled
>   by the following PCD being set to TRUE:
>   gEfiMdeModulePkgTokenSpaceGuid.PcdEnableVariableRuntimeCache
> 
> Fixes: aab3b9b9a1e5e1f3fa966fb1667fc3e6c47e7706
> 
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Michael Turner <michael.turner@microsoft.com>
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Signed-off-by: Michael Kubacki <michael.a.kubacki@intel.com>
> ---
>  MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> index b0ee5e50d0..d23aea4bc7 100644
> --- a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> +++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> @@ -16,7 +16,7 @@
>    VariableServiceSetVariable() should also check authenticate data to avoid
> buffer overflow,
>    integer overflow. It should also check attribute to avoid authentication bypass.
> 
> -Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
> +Copyright (c) 2006 - 2020, Intel Corporation. All rights reserved.<BR>
>  (C) Copyright 2015-2018 Hewlett Packard Enterprise Development LP<BR>
>  SPDX-License-Identifier: BSD-2-Clause-Patent
> 
> @@ -335,8 +335,8 @@ RecordVarErrorFlag (
>        *VarErrFlag = TempFlag;
>        Status =  SynchronizeRuntimeVariableCache (
>                    &mVariableModuleGlobal-
> >VariableGlobal.VariableRuntimeCacheContext.VariableRuntimeNvCache,
> -                  (UINTN) VarErrFlag - (UINTN) mNvVariableCache + (UINTN)
> mVariableModuleGlobal->VariableGlobal.NonVolatileVariableBase,
> -                  sizeof (TempFlag)
> +                  0,
> +                  mNvVariableCache->Size
>                    );
>        ASSERT_EFI_ERROR (Status);
>      }
> --
> 2.16.2.windows.1
> 
> 
>